1. Field of the Invention
The present invention relates to methods for efficiently separating two liquids like oil and water, flon and water or flon and oil, etc., which are different in sp. gr. from each other and which are in mixed state, and apparatuses for implementing them. For example, it pertains to apparatuses capable of e.g., oil-water separation of ship's bilge waste liquor or factory waste liquor, further, separation of impurity fluids from water to make it potable, etc., and in addition, it has as its objective providing two liquid separating apparatuses capable of making purification of the liquid to be separated left after removal of impurity liquid.
2. Description of the Prior Art
Well-known as techniques for separating two liquids being in mixed state are baffle plate system separating method, inclined plate separating method and coalescer system, etc. These methods are established on the basic principle that with obstacles or inclined plates installed in a flow path where the mixture passes, the two liquids are gradually separated in long time by the sp. gr. difference between them in the process of its passing through these obstacles or inclined plates.
However, since for example, in a mixture of oil and water in suspended state, ions are adsorbing on the colloidal particle surfaces of oil, a zeta potential due to the electric double layers is generated at their interfaces with aqueous liquid. Then due to the Coulomb' force resulting from this zeta potential, the oil particles are repelling each other, thereby maintaining their stable floatation. Particularly, in a low concentration oil-water mixture, the distance between the colloidal particles is long; therefore, the repulsive Coulomb's force is far larger than their intermolecular attraction. Accordingly, the separation of the two liquids from each other can not be made by the conventional physical means. Besides, in an oil-water mixture which is emulsified by mixing-in of a surface active agent, not only the oil particles are reduced in size, but the bonding potential of water and oil particles to each other is high; on this ground, the two liquid separation is, in principle, impossible by the conventional physical means only.
Further, conventional two liquid separating apparatuses merely have the two liquid separating function. Therefore, if the liquid to be separated left after removal of impurity liquid is to be again utilized, purifying treatment process by separately installed purifying apparatuses will become necessary. Thus problems have been raised not only that the treatment operation is confusing, but that the treating time is prolonged.